The primary aim of this study is to examine the nutritional and behavioral factors related to obesity in patients with hypothalamic tumors. The study will characterize growth, body composition, and energy balance (dietary intake, resting energy expenditure and total energy expenditure) in obese children with hypothalamic / chiasmatic gliomas and craniopharyngiomas. In addition, serial psychometric assessment of eating behaviors and obesity will be done during and after treatment for obesity.